This invention relates to improvements in apparatus for excavating and transplanting trees and similar plants, and more particularly to a vehicle-mounted apparatus having a plurality of reciprocating blades adapted to pierce the ground surrounding a tree in such a way that a well-shaped protective ball of soil about the roots of the tree is maintained intact for protection of the tree during transportation and transplanting.
In the excavation and transplanting of trees, it is important to remove as much of the tree root system as possible when moving the tree from the original growing site. In order to accomplish this, devices have been developed for positioning cutting blades around the trunk of the tree for digging into and piercing the earth surrounding the tree in a manner for removal of as large a ball of dirt with the roots as possible. Such prior devices usually have a plurality of blades which are positioned at spaced points around the tree and then hydraulically driven on converging paths into the ground to form either a conical or truncated-shaped confinement for the root system and ball of earth. When all of the blades have been driven fully into the earth, the blades and their supporting framework are simultaneously lifted upwardly thereby raising the tree and the ball of earth out of the excavation hole. The tree may then be transplanted or the ball of earth may be wrapped with burlap and wire and then moved to a remote desired location. Generally, prior machines are capable of digging and lifting a tree in less time than the tree may be manually excavated and transplanted, and with less disturbance of the earth forming the ball about the roots and thus with less damage to the root system of the tree. However, the prior devices require a relatively large area free of trees, shrubbery, and any other obstructions adjacent the plant to be moved in order to provide sufficient space for the vehicle carrying the device to maneuver into position adjacent the tree and to move the blades into their positions around the tree for the excavation thereof. While such prior devices can be maneuvered satisfactorily in open spaces, in nurseries where trees and shrubs are normally grown close together on four foot centers along adjacent rows so as to allow for the raising of the maximum number of plants in a given area, the prior devices cannot be used in many situations because there is not sufficient room to position the machine at a particular plant without damaging the adjacent plants. Moreover, because of the height and width of the prior devices, some trees and shrubs having low branches cannot be moved with the prior devices without damaging such trees and shrubs. As a result, the transplanting of many trees and shrubs must still be done by the older, manual method.
In the excavation of trees and other plants with hydraulically powered tree spades, it is essential that the blades maintain a predetermined path as they penetrate the earth and converge to define an excavation area around the root system of the tree. If the blades deviate from the designed path, the root system may be excessively damaged or the dirt ball may not remain intact, either of which will cause loss of the tree. Also, the weights of the tree spade apparatus and the vehicle must be sufficient to offset the forces created by the blades penetrating the earth; insufficient weight of the vehicle and apparatus and/or improper positioning of that weight will permit unwanted additional movement of the blades and damages to the root ball. Heretofore, a variety of apparatus have been used in an attempt to insure that the blades reciprocate smoothly and converge properly to provide a dirt ball around the tree which is the desired size and shape and, more importantly, is intact. Some prior art devices employ housings which are complex and failure-prone assemblies, including arrangements of rollers, guide blocks, flanges and groves, gears, pens and groves and wheels and rails to restrain, maintain and guide the blade along a predetermined path. See, for example, Lemond U.S. Pat. No. 4,286,398 Bates U.S. Pat. No. 3,618,234 and Stocker U.S. Pat. No. 4,031,637. Another prior device, Grover U.S. Pat. No. 3,713,234, uses a pair of telescoping tubes to guide and direct the blade along the desired path. These prior devices have not been entirely satisfactory for several reasons including durability, mechanical failure, mechanical wear and difficulty to replace parts, and the general inability of the parts to move or slide smoothly relative to one another when dirt, rocks and other debris normally found at excavation sites gets between the parts which must move or slide relative to adjacent parts. Such dirt, rocks and debris cause these prior devices to bind or jam and require frequent stops for cleaning.